The Lebanese electricity system has been evaluated in terms of its sustainability. An integrated approach was adopted to assess the life-cycle technical, environmental, energy and economic attributes of the system. The findings show that the Lebanese electricity system is characterized by a weak performance in all analysed aspects related to the sustainability of energy systems. Specifically, the system lacks adequacy and security leading to a supply-demand deficit and poor diversity. It gives rise to significant environmental emissions (including green-house gases), and produces large economic inefficiencies. The costs and benefits of optimising the performance of the centralised electricity system are presented, indicating substantial net benefits (together with considerable benefits in reduced environmental impacts across the life-cycle assessment categories, including carbon emissions) from improving the transmission and distribution networks, upgrading existing conventional plants to their design standards, and shifting towards the use of natural gas. The expected levelised cost of various energy sources in Lebanon also indicates that renewable energy sources are competitive alternatives at the present time. © 2009 Elsevier Ltd. All rights reserved.